In the disclosure of the present invention reference is mostly made to the treatment of diabetes by delivery of insulin, however, this is only an exemplary use of the present invention.
Conventional delivery devices for delivery of liquid drugs by means of subcutaneous injection typically have been provided as devices such as pen-shaped devices having a cylindrical form-factor. The cylindrical form-factor approach has mainly been chosen due to the particular use of cylindrical drug-filled cartridges. While the cylindrical form-factor generally enables design of slim devices, this form-factor typically has short-comings as regards device length and available surface area for presenting information to the user, e.g. by means of a display.
To overcome these problems, delivery devices having form-factors other than the pen-shaped form-factor have been proposed. Examples of injection devices having both the cylindrical form-factor as well as devices having a non-cylindrical form factor are disclosed in WO 98/10814.
Generally, from a users viewpoint there is a wish that the delivery device is as slim and short as possible in order to provide for a compact device which may be easily carried about, i.e. in a shirt-pocket or the like. At the same time, there is a wish that modern injection devices offer an increasingly variety of features. Such features may include a large display for presenting the size of the set dose, a large maximum dosing amount available for each single administration, automatic expelling of set doses, the prevention of setting a dose exceeding the drug amount remaining in the device, etc.
In a recent publication, WO 2011/045611 discloses a spring driven injector having a dose setting arrangement to select a dose volume and a drive mechanism which in some forms include a preloaded spring having stored energy sufficient to expel the entire useable contents of a cartridge over a succession of doses. In accordance with the teachings of WO 2011/045611 the proposed injection devices presents drawbacks having regard to building length. In addition, the proposed window arrangement for indicating set doses provides a far from user friendly design as it includes a window that rotates relative to the housing as the dose is being dialled. Furthermore, potentially unsafe situations may occur if a mechanical defect should occur within the device causing an uncontrolled expelling of the entire contents of the cartridge.
Having regard to the above discussion, it is a first object of the present invention an injection device that is superior in user friendliness compared to prior art devices.
It is a further object of the present invention to provide an injection device that is more compact than prior art devices.
It is a still further object of the present invention to provide a medical injection device that is safer in use compared to prior art injection devices.